Ni-Al2O3 and Ni-Al composite high-aspect-ratio microstructures

Tao Wang; Melford Sorrell; Kevin W. Kelly; Evan Ma

doi:10.1117/12.324077

1 September 1998 Ni-Al₂O₃ and Ni-Al composite high-aspect-ratio microstructures

Tao Wang, Melford Sorrell, Kevin W. Kelly, Evan Ma

Proceedings Volume 3512, Materials and Device Characterization in Micromachining; (1998) https://doi.org/10.1117/12.324077
Event: Micromachining and Microfabrication, 1998, Santa Clara, CA, United States

Abstract

High-aspect-ratio microstructures (HARMs) have a variety of potential applications in heat transfer, fluid mechanics, catalysts and other microelectromechanical systems (MEMS). The aim of this work is to demonstrate the feasibility to fabricate high performance particulate metal-matrix composite and intermetallic micromechanical structures using the LIGA process. Well-defined functionally graded Ni-Al₂O₃ and Ni-Al high-aspect-ratio microposts were electroformed into lithographically patterned PMMA holes from a nickel sulfamate bath containing submicron alumina and a diluted Watts bath containing microsized aluminum particles, respectively. SEM image analysis showed that the volume fraction of the alumina reached up to around 30% in the Ni-Al₂O₃ deposit. The Vickers microhardness of these composites is in the range of 418 through 545, which is higher than those of nickel microstructures from a similar particle-free bath and other Ni-based electrodeposits. In the work on Ni-Al electroplating, a newly developed diluted Watts bath was used to codeposit micron-sized aluminum particles. The intermetallic compound Ni₃Al was formed by the reaction of nickel matrices and aluminum particles through subsequent annealing at 630 degrees Celsius. WDS and XRD analyses confirmed that the annealed coating is a two-phase (Ni-Ni₃Al) composite. The maximum aluminum volume fraction reached 19% at a cathode current density of 12 mA cm^-2, and the Vickers microhardness of the as-deposited coatings is in the range 392 - 515 depending on the amount of aluminum incorporated.

Citation Download Citation

Tao Wang, Melford Sorrell, Kevin W. Kelly, and Evan Ma "Ni-Al₂O₃ and Ni-Al composite high-aspect-ratio microstructures", Proc. SPIE 3512, Materials and Device Characterization in Micromachining, (1 September 1998); https://doi.org/10.1117/12.324077

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